1. Field
The disclosure relates to techniques for utilizing negative current sense feedback in a buck converter.
2. Background
Buck converters are commonly used in electrical devices to step down a voltage from a first level (e.g., from a battery source) to a lower second level. In typical applications, buck converters source current to a load, and are not usually configured to sink current from a load. In these applications, when it is desired to decrease the target output voltage level of the buck converter, the buck converter will reduce the current sourced to the load, or stop providing current to the load, thus relying on the load to eventually discharge the output voltage to the desired value. If the load resistance is small, then it could take a long time for the output voltage to be discharged to the lower target level.
In one prior art implementation of a current mode buck converter (e.g., one that forces a continuous condition mode, or CCM), the inductor current is allowed to go negative during a “reverse boost mode.” In reverse boost mode, the inductor can draw current away from the load, thereby allowing the buck converter to discharge the load more quickly. In such prior art implementations, however, the inductor current can grow increasingly negative without bound. Furthermore, when the output voltage reaches the lower target level, the negative inductor current would still need to be brought back to a positive level to drive the load. This undesirably causes undershoot, and prolongs the settling time of the system.
It would be desirable to provide techniques for configuring a buck converter in reverse boost mode to reduce output voltage undershoot and settling time during target level transitions.